Megaflo scale problems - advice required on descale.

[Dave_79]

Hello and happy new year.

I'm not a plumber, I know you need an unvented ticket to do this work, I've done all I can, I'm just looking to clue up so I know the job will be done right.

Megaflo 210i Unvented Indirect cylinder installed in new build house 7 years ago. Problems just started in the last 6 months. Large deposits of scale found in all hot tap filters throughout the house. It destroyed the thermostatic bath safety mixer device which has now been removed. Slightly hard water area - kettle needs doing every 3 months. None of the neighbours with the same kit seem to have any issues.

No issues on the cold take-off at all. Cylinder and Boiler working properly, all safety valves OK and the strainer in the pressure reducing valve is totally clean.

Tank stat was set on factory 68 degrees all it's life and the boiler run 3 times a day for 1 hour. Immersion is working but has never been used. To investigate I changed the tank stat to max (80 deg) and ran the boiler 24/7 which seemed to make it worse. Right now the tank stat is on low (50-60 deg) and boiler on 24/7. Seems slightly better but every day you can hear a dump of scale come down and clog up whatever outlet is in use. Mixer showers are particularly bad and I'm removing them constantly cleaning the filters. I could be wrong but it seems to happen more during long showers, or when two outlets are used at once. Sometimes you'll get a week totally clean but it always comes back.

So I assume the tank is very scaled up. The immersion probably wants replacing as I hear they scale up first, but I'm wondering if a power flush is in order? Is it Fernox DS-3 for this? Anyone done this kind of thing? Do i need a power flush or just some DS-3 deposited into the cylinder outlet and let it do it's thing? I've also head of people having it hoovered out through the immersion hole if it's too bad (which i'm guessing it is).

Any advice greatfully received on the way forward, or what could have caused this?

Thanks...

 

[picasso]

I don't think that is scale, is there any smell to the hot water ? if there is it could be a bacterial growth.

 

[Dave_79]

No smell noticeable no... but that's worrying.

It sure looks like scale, and is hard. When a larger lump is left out of water it does have a greenish tinge to it and goes brittle, like limescale. The 2nd pic is the only time I've seen it like that... most times it looks like the 1st pic.

Having said that I tried to dissolve some bits of it in boiling 'Oust' which works wonders on our kettle and it didn't touch it.

 

[dilalio]

I'd give megaflo a call and ask their thoughts on it. It may be a known issue with air bubble components inside the cylinder reacting with the water.

 

[picasso]

As dilalio says it could be the plastic ring that makes the bubble breaking down.

 

[Dave_79]

Thanks. I'll definitely drop Megaflo a line tomorrow and will be engaging a qualified plumber in any case... but it's definitely not plastic. Does appear to be limescale to me as it goes chalky when it dries.

For what it's worth the bubble seems to be behaving normally - just the usual annual air replenish required and no overflow from the tundish.

 

[picasso]

If it was limescale the boiling oust would dissolve it , must admit I have never seen anything like it.

 

[John D v2.0]

Have your checked the boiler primary temperature? Maybe your primary water is 85c and the neighbours is 65c? Hotter would make more lime scale.
Another option to protect the rest of your plumbing is to fit a suitable strainer on the outlet, then there's only one place to clean and reduce damage to the tap seatings.

 

[Dave_79]

Good shout on the strainer I'll have a look about. Primary boiler temp was always max (80) but since I've dropped the tank stat to halfway I've had it at 65. Will have a play in both directions and see if it makes any odds, but I fear the damage is now done and I'm fighting an endless battle against it tbh.

I was very surprised the Oust didn't touch it in my test container. Also got some crystals donated to me by a friend who's a facilities manager. Can't remember the name - he said it was the active ingredient in Oust and it's what they use in the commercial tanks, still didn't even slightly dissolve a tiny piece! Which is why I'm doubting if Fernox DS-3 will work. Don't want to end up replacing the tank as we're moving soon!


Thanks for everyones input...

 

[Dave_79]

Just to add... in late summer I flushed the tank through 3 times. There was a tiny bit of the crud came out with it but nothing like what I was expecting. Refilled the tank and let it settle but was plagued with deposits for a few days afterwards whenever we used taps or showers. Seems to be affecting the hot water outlet at the top of the tank.

 

[dilalio]

I'd be interested to find out what that is.
Maybe see if your water provider would test it for you, they might actually be keen to do so as their product is part of the process causing it. Give them a call or stop one of their guys in the street next time you see a van.

Edit: you could also try WRAS.

 

[snb]

Do you have watersoftener or have had one or a phosphate kit?

 

[Dave_79]

Hi... nope nothing like that. Just a standard new build installation. Probably installed as quick as possible and not flushed through properly, but I can't see how that would cause issues 6 years later. If we were staying I'd already thought a water softener might be required though. There was something on a local Facebook group a while ago about our supply being changed to harder water and people were complaining about frothy cups of tea - could be related I suppose but surely the neighbours would have had symptoms by now. When it clogs the shower it completely blocks it - and I haven't noticed any plumbers vans around!

 

[muggles]

Good shout on the strainer I'll have a look about. Primary boiler temp was always max (80) but since I've dropped the tank stat to halfway I've had it at 65. Will have a play in both directions and see if it makes any odds, but I fear the damage is now done and I'm fighting an endless battle against it tbh.

I was very surprised the Oust didn't touch it in my test container. Also got some crystals donated to me by a friend who's a facilities manager. Can't remember the name - he said it was the active ingredient in Oust and it's what they use in the commercial tanks, still didn't even slightly dissolve a tiny piece! Which is why I'm doubting if Fernox DS-3 will work. Don't want to end up replacing the tank as we're moving soon!


Thanks for everyones input...

Don't drop the cylinder stat too low - the hot water needs to be stored at 60°C to prevent legionella formation

 

[John D v2.0]

Don't drop the cylinder stat too low - the hot water needs to be stored at 60°C to prevent legionella formation

Agree although technically that only has to happen once a week it doesn't need to be permanently stored at 60 degrees 24hours a day